A cell-free system capable of the complete de novo synthesis of an active antibody molecule will allow a detailed investigation of the role of post-translational modification of immunoglobulin heavy and light chains in the synthesis, assembly, intracellular transport and secretion of immunoglobulin molecules. This proposal describes experiments designed to construct such a system. Murine plasmacytoma cell lines which produce immunoglobulin molecules with an antibody-like affinity and biospecificity for various chemical groups, will serve as the experimental system. Initially, the immunoglobulin heavy and light chain messenger RNAs will be purified. Various methods of subcellular fractionation will then be investigated in order to localize and purify the enzymatic activities responsible for the post-translational processing of immunoglobulin protein chains. These cellular components will be incorporated into a cell-free protein synthesizing system in order to carry out proteolytic precursor cleavage and specific, sequential glycosylation on the newly synthesized immunoglobulin polypeptides. The biological activity and the degree of assembly of the cell-free product will be measured. The information obtained in this study should be applicable to an examination of the synthesis and assembly of other complex biological structures with specialized functions.